Printing machines, such as rotary offset lithographic duplicating machines, rotary printing presses, or the like normally include a printing couple which comprises a number of cylinders and/or rollers for supplying ink from a reservoir. In offset lithographic machines, moisture also is supplied from a reservoir. The machine includes a printing couple which comprises a number of cylinders and/or rollers such as impression cylinders, master cylinders, blanket cylinders, form rollers, ductor rollers, transfer rollers and the like. Such duplicating machines have been known and used for many years and, today, have become rather sophisticated in high-speed duplicating or printing processes.
An important area in which such duplicating machines have found wide utility is in short run printing. Short run printing jobs encompass a wide range of applications where printing is needed for several hundred sheets, for instance, versus more production oriented applications where the machine is set up and thousands of sheets are duplicated, such as in printing magazines, advertising brochures or the like.
An example of a "short run" duplicating application is in printing bank checks, deposit slips and the like. Every bank employs a particular printing company which prints checks and deposit slips for its customers. The checks usually come in standard styles and a machine may be set up to print a given style with the appropriate repeating indicia thereon. However, for each customer order, which may constitute only a few hundred checks, each check must be imprinted with the name of the bank, the name and address of the customer, the customer's deposit account number, as well as serially printing the check numbers, in order, as a printing run proceeds. In order to avoid excessive costs and resulting charges for such short run printing jobs, printing concerns and duplicating machine manufacturers constantly are endeavoring to design new and improved systems, attachments or mechanisms to speed up change-over procedures from one printing run to the next.
Another example of short run printing is in the area of imprinting different identifications, logos, or the like which may vary but which must be imprinted along with other more permanent identification indicia. Letterheads are but one example. A large company, such as an insurance company, may have a standard letterhead form for the parent company. However, the company may have many, many branch offices around the country. Each standard letterhead form must be imprinted, again in short runs, to continuously supply stationery to the branch offices, with the branch office identification imprinted thereon. Still further, each branch office may have separate stationery for many individuals employed or working in that office, and the stationery must be imprinted further with an individual's name and position.
A further example of short run printing is in the area of encoding. Department stores and grocery stores, for instance, now have coded price labels (i.e. encoding bars) which are printed in large volumes but with many different price codes. There may be many labels on a single printing sheet, resulting in the printing machine employing a multiplicity of individual printing heads on a single roller or shaft for printing the labels.
These are but some examples of the wide range of short run duplicating situations where rapid changing of printed indicia is necessary.
As stated above, most duplicating machines of the character described employ many different types of rollers, all of which are precisely positioned and aligned in parallel to effect high quality, rapid printing. Therefore, providing a system for rapid interchanging of printing heads for short run duplicating situations involves high precision techniques. Usually, the printing heads are mounted on a rigid shaft or roller adjacent the ink fountain rollers of the machine. Some prior machines simply have the interchangeable or adjustable printing heads, for short run printing, mounted directly on the permanent shaft. Each time the printing heads have to be changed, in order to change or reset the numbers, change to another office or individual's name, or change a price code, the machine had to be shut down to make the adjustments. It can be seen that with some short run printing situations, the machine downtime would be as much as its production time.
Other attempts have been made to provide for interchanging the machine shaft itself. However, it must be kept in mind that such precision shafts are very heavy and, in combination with the printing heads and mounting brackets associated therewith, can even be too heavy and cumbersome for some individuals to handle. In addition, interchangeable shafts create tolerance problems. A shaft in quality duplicating machines often must be maintained within thousandths or tens of thousandths of an inch in tolerances. Interchangeable shafts simply cannot maintain this precision, much less avoid disturbing micro-switches, timing cams, etc. which are associated with the shaft. These mechanisms must be uncoupled and, in essence, such prior procedures literally constitute a type of dismantling of the machine, even though they allow for adjusting or interchanging the printing heads off of the machine while another printing run is being performed. Still, the downtime in dismantling and removing a shaft assembly is considerable, in addition to the lack of quality printing which is often encountered.
This invention is directed to solving the above problems and satisfying the continuing need for providing rapid changing of printed indicia in duplicating or printing machines.